The use of airbreathing devices in the first phase of an acceleration/launch mission provides several advantages with respect to traditional solid rocket motors, including consistent savings in terms of payload and costs. In a ducted rocket, fuel-rich combustion products of an oxidizer-lean propellant burning in a gas-generator, are ejected in the ramburner, where the introduction of atmospheric air completes the oxidation. As a part of the ducted rocket systems, the fuel-rich propellant becomes a critical component, especially when metalized compositions are introduced. This work presents a research activity focused on the combustion behavior of some fuel-rich formulations based on aluminum. After a theoretical evaluation of performances, combustion tests investigating the burning rate and condensed combustion products are performed.